Stick insects (order Phasmatodea) are not generally considered dangerous to humans. These creatures are masters of camouflage, primarily relying on their resemblance to twigs or leaves to avoid detection by predators. The answer to whether they are poisonous is a definitive no for the vast majority of species worldwide. Their slow-moving, herbivorous nature means they are typically harmless and pose no threat to people or pets.
Understanding Poisonous and Venomous
To accurately assess the risk posed by any creature, it is important to distinguish between “poisonous” and “venomous.” A venomous animal, such as a spider or snake, actively injects a toxin into a victim, usually through a bite or a sting. Stick insects lack any venom apparatus, like fangs or stingers, and therefore cannot inject toxins.
A poisonous animal contains toxins that are harmful if they are ingested or absorbed through skin contact. While a few stick insect species possess chemical defenses, the insects themselves are not poisonous. They do not have toxic flesh, and ingestion of most species would likely result only in mild digestive upset. The potential for harm comes from a defensive secretion released when the insect is disturbed, not from a toxin in the insect’s body.
Defensive Chemical Sprays
A notable exception to the harmless nature of stick insects is found in certain species that employ a chemical defense. Some New World species, particularly those within the Anisomorpha genus, such as the two-striped walkingstick (Anisomorpha buprestoides), utilize this mechanism. When threatened, these insects can accurately spray a defensive compound from specialized glands located on their prothorax. This secretion is a deterrent, not a poison, designed to repel predators through irritation.
The primary active compound in the spray is often anisomorphal, a monoterpene dialdehyde that functions as a highly irritating agent. This chemical acts as a contact repellent, causing immediate, intense pain upon exposure to sensitive membranes. If the spray contacts the eyes, it can result in temporary blindness, conjunctivitis, and, in severe cases, corneal ulceration. The insect can project this foul-smelling liquid up to 40 centimeters, often aiming for the eyes of the perceived threat.
Safe Interaction and Handling
Caution is warranted when interacting with stick insects, especially those in the genus Anisomorpha, due to their irritating chemical sprays. The safest practice is to avoid handling any wild stick insect that you cannot positively identify as harmless. If handling a stick insect, encourage it to walk onto an open hand rather than attempting to grasp or squeeze its body.
Always wash your hands thoroughly with soap and water immediately after contact, particularly before touching your face, eyes, or mouth. Supervision is recommended if children or pets interact with these insects, as they are more likely to trigger the defensive spray. If accidental eye exposure occurs, the affected area should be flushed immediately with copious amounts of clean water to mitigate the painful effects of the chemical compound.